Presence and Availability Management (PAM) tools provide presence information to users of PC-based interfaces (e.g., via user-specified “buddy” lists). Such tools are common in Instant Messaging (IM) systems and may be applied to a variety of devices and contexts, including email systems, Personal Digital Assistants (PDA's), text-based or graphical-visual displays offered in cellular phones and Session Initiation Protocol (SIP) or other Voice Over Internet Protocol (VoIP) telephones.
However, audio-centric devices, such as traditional Public Switched Telephone Network (PSTN) telephones, do not typically provide presence information directly to device users. While presence may be inferred in some instances (e.g., via certain telephones that visually indicate the availability of one or more telephone lines), a PSTN user typically does not receive presence information until attempting to place a call. The user may then hear ringing, a busy signal, or a message intercepting the call, each alternative providing some evidence as to a called party's availability, but only after the caller has expended valuable time and energy in placing the call.
Similarly, while mobile phones and VoIP phones may include instant messaging information, they do not indicate whether remote parties are available to receive calls. Consequently, callers initiate calls without a priori knowledge of whether intended recipients are available to receive them. In many cases, a caller does not reach a called party directly, and instead receives a voicemail greeting, a busy signal, or no answer, each potentially wasting the caller's time and effort in having placed the call.
Thus, there is a need for improved techniques of presenting and utilizing presence information via telephones and other communication devices.